Scroll fluid machine

ABSTRACT

A scroll fluid machine comprises a housing, two fixed scrolls each of which is fixed on each side of the housing, an endless transmitting member connected to an electric motor, a driven pulley wound by the transmitting member, a thrust-offsetting shaft rotatably mounted at a position eccentric from a axis in the driven pulley, two orbiting scrolls each of which is fixed at each end of the thrust-offsetting shaft which rotates to form a compression chamber with the fixed scroll, and a self-rotation preventing device disposed between the housing and the orbiting scroll.

BACKGROUND OF THE INVENTION

The present invention relates to a scroll fluid machine suitable as an air compressor and a vacuum pump.

In JP2000-130365A, a scroll fluid machine comprises a casing, a fixed scroll fixed at each side of the casing, an electric motor in the casing, an eccentric bearing disposed between the electric motor and the fixed scroll, a rotational shaft that rotates together with an intermediate wheel of the eccentric bearing with a rotor of the electric motor, an orbiting shaft that rotates together with an inner wheel of the eccentric bearing, an orbiting scroll fixed to the orbiting shaft to form a compression chamber with the fixed scroll at each side, and a self-rotation preventing device provided between the orbiting scroll and a stationary member.

In JP2006-183561A, an orbiting scroll is rotatably supported on each end of a single eccentric shaft rotatably mounted in a casing. An eccentric shaft is connected to an electric motor via an endless belt and driven with the belt.

In the scroll fluid machine in JP2000-130365A, a compressor for compressing fluid such as air sucked from an inlet is constructed together with the electric motor for driving the compressor. For example, when a scroll compressor for which AC frequency is set to 50 Hz in the Eastern Japan is used in the Western Japan where AC frequency is set to 60 Hz and when it is used in other countries where voltage is higher that that in Japan, the number of rotation of the AC electric motor gets higher. In order that the compressor is not overloaded, it is necessary to change the length of a tip seal for sealing the compression chamber and to replace the electric motor with a new one. The fixed scrolls, orbiting scrolls, eccentric shaft bearing and electric motor are arranged side by side to make its length larger.

In the scroll fluid machine in JP2006-183561A, the eccentric shaft is driven with the belt. By changing a diameter of a pulley of the electric motor, rotation speed of the orbiting scroll can be easily changed. Between the orbiting scroll and the end of the eccentric shaft, a bearing for rotatably supporting the orbiting scroll on the eccentric shaft is disposed, so that axial length gets larger. It would be very difficult to offset thrust loads acting the right and left orbiting scrolls securely.

SUMMARY OF THE INVENTION

In view of the disadvantages, it is an object of the invention to provide a scroll fluid machine that responds to difference in AC frequency and voltage, thrust acting to right and left orbiting scrolls being efficiently offset.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a scroll fluid machine according to the present invention;

FIG. 2 is a vertical sectional view taken along the line II-II in FIG. 1;

FIG. 3 is a vertical sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a perspective view of the scroll fluid machine and a motor in which a belt is removed from driven and driving pulleys and a reinforcement member is removed from a housing; and

FIG. 5 is a perspective view of the scroll fluid machine in which the drive pulley is connected to the driving pulley via the belt.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

One embodiment of the present invention will be described with respect to the drawings.

In FIGS. 1 and 3, at each side of a cylindrical housing 1 of a scroll fluid machine, a fixed scroll 2 which includes a fixed wrap 21 is fixed with a plurality of screws. L-shaped feet 20, 20 which are fixed on a support (not shown) are fixed to the lower part of the housing 1.

On the inner side surface of the fixed scroll 2, a spiral orbiting scroll 3 which has a spiral orbiting wrap 31 engages with the fixed wrap 21 to form a compression chamber so as to rotate around the first axis O1.

The right-hand orbiting scroll 2 is disposed on the inside of the housing 1 with three known pin-crank-type self-rotation preventing devices 30 spaced on a circle by 120 degrees. Only one of the self-rotation preventing devices is shown in FIG. 3. In this embodiment, the right and left orbiting scrolls 3, 3 are fixed at the right and left ends of a thrust offsetting shaft 10. Thus, the pin-crank-type self-rotation preventing device 30 may be provided only on the right-hand orbiting scroll 3, allowing the left orbiting scroll 3 to orbit.

In a cylindrical cover la in the middle of the housing 1, between orbiting scrolls 3 and 3, a cylindrical driven pulley 5 on which a transmission belt 6 is wound is rotatably supported.

The driven pulley 5 comprises a cylindrical axial portion 51 pivotally mounted in bearing holes 1 b, 1 b in the housing 1 via ball bearings 4, 4; and a pulley portion 52 fixed on the outer circumference of the cylindrical axial portion 51. A belt 6 is wound on the outer circumference of the pulley portion 52. The driven pulley 52 is pivotally mounted in the housing to rotate around the first axis 01.

The transmission belt 6 is wound on the driven pulley 5 and a driving pulley 8 provided on an output shaft of an outer electric motor 7. The rotation of the outer electric motor 7 is transmitted to the driven pulley 5 via the driving pulley 8 and the transmission belt 6. The driven pulley 5 rotates around the first axis O1.

The driven pulley 5 comprises a balance weight 53 for making rotation of the orbiting scroll 3 smooth. The balance weight 53 is part that is larger in thickness and width than the other parts comprising a cylindrical axial portion 51 and pulley 52.

In a through hole 54 of the axial portion 51 of the driven pulley 5, a thrust-offsetting shaft 10 is rotatably supported via a roller bearing 9. The thrust-offsetting shaft 10 rotates around the second axis O2 deviating radially from the axis O1 with respect to the driven pulley 5. As the driven pulley 5 rotates, the thrust-offsetting shaft 10 rotates around the second axis O2.

At the ends projecting from right and left roller bearings 9, 9 of the thrust-offsetting shaft 10, bosses 32, 32 at the center of the right and left orbiting scrolls 3, 3 are fixed to rotate together with the thrust-offsetting shaft 10. Thus, opposing thrust loads which act on the right and left orbiting scrolls 3, 3 are offset by the thrust-offsetting shaft 10.

When the driven pulley 5 rotates around the first axis O1 with running of the belt 6, the thrust-offsetting shaft 10 rotates together with the orbiting scrolls 3, 3 around the second axis O2. When the right and left orbiting scrolls 3, 3 rotate, volume of a compression chamber defined by the fixed wraps 21, 21 and orbiting wraps 31, 13 gradually reduce toward the center from the outer circumference. External air sucked via inlets 22, 22 of the outer circumference of the fixed scrolls 2, 2 is gradually compressed toward the center and discharged from outlets 23, 23 at the center of the fixed scrolls 2, 2. During compression of sucked external air, thrust loads acting onto the right and left orbiting scrolls 3, 3 are offset by the thrust-offsetting shaft 10, thereby assuring smooth rotation of the right and left orbiting scrolls 3.

At the upper part of a cover 1 a of the housing 1 or side opposite a feet 20, there is formed an opening 1 c with which the belt 6 is wound on the driven pulley 5 from the outside of the housing 1. In FIG. 2, at the lower part of the cover 1 a having no opening, there is formed a connection 1 e for connecting the right and left fixed scrolls 2, 3. At the ends of the connection 1 e facing the inner surface of the belt, reliefs 1 d, 1 d close to the belt 6 are formed substantially in parallel with a running direction of the belt 6.

By forming the upper opening 1 c of the housing 1 in FIG. 4, an only reinforcement member 12 (later described) is removed from the housing 1, thereby facilitating removal of the belt 6 from the driven pulley 5 through the opening 1 c to carry out efficient replacement and inspection to the belt 6. The opening 1 c is formed at the opposite side of the feet 20. Thus, the feet 20 do not obstruct replacement of the belt 6. While the feet 20 are still fixed on a support, the belt 6 can be replaced with a new one. The relief 1 d is provided at each end of the connection 1 e, preventing the belt 6 from getting in touch with the cover 1 a and keeping an area of the opening 1 c at minimum. Furthermore, the relief 1 d of the connection 1 e is close to the inner surface of the belt 6. Thus, during running of the belt 6, the connection 1 e is cooled by turbulent flow of air generated around the belt 6, and the cover la and the right and left housings can be cooled by the cover 1 a.

At the upper part of the cover 1 a of the housing 1 or at the opposite side to the connection le around the axis O1, a plate-like reinforcement member 12 is detachably fastened with a plurality of screws 11 to cover the opening 1 c. During running of the scroll fluid machine, the reinforcement member 12 prevents deformation of the housing 1 expanding the opening 1 c when load is applied as shown by arrows “A” to the housing 1 by outward force acting to the right and left fixed scrolls 2, 2 thereby assuring secure engagement of the fixed wraps 21, 21 with the orbiting wraps 31, 31, reducing wear of sliding parts and preventing decrease in compression efficiency. The reinforcement member 12 can be detachably mounted with the screws 11 to the housing 1, facilitating replacement and inspection to the belt 6.

In this embodiment, the reinforcement member 12 comprises a flat plate. Instead, the reinforcement member 12 may be curved to cover the whole area of the opening 1 c. A plurality of heat-releasing holes may be formed in the reinforcement member 12 if the reinforcement member 12 is curved.

In this embodiment, the endless belt 6 is provided. Instead of the belt, a chain may be used. 

1. A scroll fluid machine comprising: a housing; two fixed scrolls each of which is fixed to each side of the housing and has a fixed wrap; an endless transmitting member connected to an external electric motor; a cylindrical driven pulley disposed between the two fixed scrolls in the housing and rotating around a first axis by the electric motor via the transmitting member; a thrust-offsetting shaft rotating around a second axis deviating from the first axis of the pulley; two orbiting scrolls each of which has an orbiting wrap and revolves with the thrust-offsetting shaft which offsets thrusts acting to the two orbiting scrolls, the thrust-offsetting shaft rotating with rotation of the driven pulley to form a compression chamber between the fixed wrap and the orbiting wrap engaging with each other; and a self-rotation-preventing device disposed between the housing and the orbiting scroll, the thrust-offsetting shaft rotating to allow the orbiting scroll to orbit while the orbiting scroll is prevented by the self-rotation-preventing device from rotating on the second axis.
 2. The scroll fluid machine of claim 1, further comprising a bearing for supporting the thrust-offsetting shaft rotatably in the driven pulley.
 3. The scroll fluid machine of claim 1 wherein a cover for covering an outer circumference of the driven pulley in the housing has an opening enabling the transmitting member to be wound on the driven pulley from outside of the housing.
 4. The scroll fluid machine of claim 3 wherein a part that has no opening of the cover acts as a connection connecting the two fixed scrolls, a relief being formed close to and in parallel with an inner surface of the transmitting member.
 5. The scroll fluid machine of claim 3 wherein a reinforcement member is provided in the cover of the housing to cover the opening.
 6. The scroll fluid machine of claim 1 wherein the transmitting member comprises a belt. 